1. Field of the Invention
The present invention relates to a loudspeaker diaphragm and a loudspeaker using the same.
2. Description of the Related Art
In general, a vibration system member, such as a loudspeaker diaphragm to be used in a loudspeaker, is obtained by assembling respective members, such as a diaphragm, an edge, and a gasket, each molded into a predetermined shape, using an adhesive. The vibration system member thus obtained has a problem in that poor bonding may be caused depending on the combination of the respective members, and a problem in that characteristics may fluctuate due to a variation in adhesive application amount. Further, in order to prevent an operation failure of the loudspeaker, it is necessary to use a highly-accurate assembly jig, which leads to a problem of poor productivity. In addition, in a case of using a less adhesive material (for example, olefin-based thermoplastic resin), a process such as primer application is further required prior to adhesive application, which leads to problems with productivity and production cost.
In order to solve the above-mentioned problems, integral molding of the diaphragm, the edge, and the gasket by a double molding method has been proposed (Japanese Patent Application Laid-open No. Hei 7-15793). However, the loudspeaker diaphragm obtained in this way has a problem in adhesion between the diaphragm and the edge at the time of large amplitude.
Further, in the double molding method, thermoplastic elastomers capable of being injection molded are mainly used as edge-forming materials. However, in a loudspeaker which is configured with only an edge as a suspension without the use of a damper (e.g., micro-speaker), it is necessary to reduce hardness (increase flexibility) of the edge itself in order to broaden low-frequency reproduction. Thus, there was a limit to balance hardness, strength and elongation for conventional thermoplastic elastomers.
In contrast, it has been proposed that a low-hardness speaker edge is formed by a specific thermoplastic elastomer (Japanese Patent Application Laid-open No. 2009-65476). However, while the edge formed by this thermoplastic elastomer has an improved heat resistance and an improved weather resistance, there is a problem that adhesion of the edge to a diaphragm is reduced, and thus resulting in reduced durability.